1. Field of the Invention
The present invention relates to a disk drive, and, in particular, to a small-sized disk drive and a head suspension unit loaded in a small-sized computer.
Recently, reduction in thickness, improvement in a processing performance and improvement in shock resistance in consideration of erroneous dropping are demanded for a portable small-sized computer. For a 2.5-inch-size magnetic disk drive which is loaded in a portable small-sized computer, not only reduction in thickness but also a large storage capacity in response to improvement in a CPU""s processing performance, and superiority in shock resistance such that, when the computer is erroneously dropped, an arm supporting a head slider is prevented from hitting a magnetic disk are demanded.
In order to increase the storage capacity without increasing the size of the magnetic disk, it is necessary to reduce the pitch of the recording tracks and thus increase the number of the recording tracks. When the pitch of the recording tracks is reduced from 3 xcexcm which is the pitch in the current magnetic disk to 1 xcexcm, for example, it is necessary to improve the positioning accuracy of the head slider to the order of nanometers. In order to improve the positioning accuracy of the head slider, it is necessary to reduce the amplitude of vibration in directions parallel to the data recording surface of the magnetic disk (directions in which the head slider performs the seeking operation) of the arm supporting the head slider when resonance occurs. For this purpose, it is necessary to increase the resonance frequency of the vibration by improving the rigidity of the arm.
In order to improve the shock resistance, it is necessary to reduce the amount of bending of the arm in the direction in which the extending end of the arm approaches the magnetic disk, by improving the rigidity of the arm.
2. Description of the Related Art
A 2.5-inch-size magnetic disk drive 10 in the related art has an arrangement, as shown in FIGS. 1A and 1B, in which two 2.5-inch-size magnetic disks 12-1, 12-2 are assembled in a housing 11, these magnetic disks being rotated by a motor (not shown in the figures). Further, a head suspension unit 13 is assembled in the housing 11, the head suspension unit 13 being rotated by an actuator 14. FIG. 1B shows a magnified sectional view taken along the Bxe2x80x94B line shown in FIG. 1A.
As shown in FIG. 2, in the head suspension unit 13, an arm 21-1, a spacer 22-1, an arm 21-2, an arm 21-3, a spacer 22-2 and an arm 21-4 are fitted around a sleeve 20, are stacked in the stated order, and are fixed by a screw member 23. The sleeve 20 is assembled around a fixed central shaft 25 via bearings 24-1, 24-2 so that the sleeve 20 can rotate.
At the extending ends of the arm 21-1 through 21-4, suspensions 26-1 through 26-4 are fixed, respectively. At the extending ends of the suspensions 26-1 through 26-4, head sliders 27-1 through 27-4 are fixed, respectively.
The arm 21-1 is positioned below the magnetic disk 12-2, the arms 21-2, 21-3 are positioned between the magnetic disks 12-1 and 12-2, and the arm 21-4 is positioned above the magnetic disk 12-1. The head slider 27-1 is in contact with the bottom surface of the magnetic disk 12-2, the head slider 27-2 is in contact with the top surface of the magnetic disk 12-2, the head slider 27-3 is in contact with the bottom surface of the magnetic disk 12-1 and the head slider 27-4 is in contact with the top surface of the magnetic disk 12-1.
The vibration-frequency responding characteristics in directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending ends of the respective arms 21-1 through 21-4 in the condition where the suspensions and head sliders are attached thereto in the above-described head suspension unit 13 will now be considered.
In FIG. 8, the curve II indicated by the broken line shows the vibration-frequency responding characteristics in the directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending ends of the upper arm 21-1 and the lower arm 21-4 when a test the same as that which will be described later is performed. The peak P2 appears at the frequency f2 and the amplitude of the peak P2 is L2.
Both the vibration-frequency responding characteristics in the directions parallel to the data recording surface of the magnetic disks (the directions in which the head sliders perform the seeking operation) of the extending end of the arm 21-2 and the vibration-frequency responding characteristics in the directions parallel to the data recording surfaces of the magnetic disks (the directions in which the head sliders performs the seeking operation) of the extending end of the arm 21-3 are the same as those shown by the curve II indicated by the broken line. This is because the arms 21-2 and 21-3 merely lie on top of one another.
The frequency f2 is somewhat low and the amplitude L2 is somewhat high. This feature can be obtained both in the resonance characteristics of the vibration of the arm in the directions parallel to the data recording surfaces of the magnetic disks and in the resonance characteristics of the vibration of the arm in the directions perpendicular the data recording surfaces of the magnetic disks. Therefore, improvement in the positioning accuracy of the head sliders is difficult, and, also, it is difficult to reduce the pitch of the recording tracks, increase the number of recording tracks, and, thus, increase the storage capacity of the magnetic disks.
Further, because the arms 21-2 and 21-3 merely lie on top of one another, due to variation in dimension accuracies of the arms, variation in assembling, and so forth, there is a case where extending-end portions of the arms 21-2 and 21-3 are in contact with one another, as shown in FIG. 3A, and, also, there is a case where the extending-end portions of the arms 21-2 and 21-3 are away from and are not in contact with. one another, as shown in FIG. 3B, depending on particular magnetic disk drives 10. In FIG. 3B, a space 28 is present between the arms 21-2 and 21-3. Such variation in the assembling condition results in variation in the vibration characteristics of the head suspension unit 13. Therefore, the servo circuit for performing the seeking operation should be designed in consideration of safety for preventing the servo system from oscillating. Also in this view point, it is difficult to improve the positioning accuracy of the head sliders, and, therefore, to increase the storage capacity of the magnetic disks.
A case where the magnetic disk drive 10 is erroneously dropped onto a floor will now be considered.
Due to a shock when the magnetic disk drive 10 is dropped onto a floor, a force F is applied to the extending end of each of the arms 21-1 through 21-4, which force F depends on the weight of a respective one of the head sliders 27-1 through 27-4.
Each of the top arm 21-4 and the bottom arm 21-1 bends as shown in FIG. 4A, and the bending amount of the extending end thereof is xcex42.
Similarly, each of the intermediate arms 21-2 and 21-3 bends as shown in FIG. 4B, and the bending amount of the extending end thereof is also xcex42.
In order to reduce the thickness of the magnetic disk drive 10, the space xe2x80x98gxe2x80x99 between the magnetic disks 12-1 and 12-2 is approximately 1.8 mm, and, thus, is small. Also, the space xe2x80x98axe2x80x99 between the extending end of each of the arms 21-1 through 21-4 and a respective one of the magnetic disks 12-1 and 12-2 is approximately 300 xcexcm, and, thus, is small (see FIG. 1B). Therefore, it is difficult to reduce the thickness of each of the arms 21-1 through 21-4. As a result, when the magnetic disk drive 10 is dropped to a floor, there is a possibility that the bending amount xcex42 is so large that the extending ends of the arms 21-1 through 21-4 hit the magnetic disks 12-1 and 12-2.
When the extending ends of the arms 21-1 through 21-4 hit the magnetic disks 12-1 and 12-2, dust is produced, a head crash is likely to occur, and the data recording surfaces of the magnetic disks 12-1 and 12-2 may be damaged.
Further, there is a case where, when the magnetic disk drive 10 is dropped onto a floor, as shown in FIG. 4C, the arms 21-2 and 21-3 bend so as to be away from one another. Then, the arms 21-2 and 21-3 approach one another and hit one another. Also at this time, dust is produced.
Thus, the magnetic disk drive having the above-described arrangement is also problematic in view of the shock resistance.
Increasing the thickness of each arm in order to improve the shock resistance can be considered. However, when the thickness of each arm is increased, because the space xe2x80x98gxe2x80x99 between the magnetic disks 12-1 and 12-2 cannot be increased, it is necessary to provide one intermediate arm, instead of the two intermediate arms, the suspensions and head sliders being provided on both surfaces, respectively, of the one intermediate arm. In this case, if it is determined that only one of the two head sliders on the one intermediate arm is defective when testing for recording and reproducing a signal is performed using a test disk which is scanned by the head sliders, this intermediate arm cannot be used in the head suspension unit. Thus, the productivity of the head suspension unit is not high.
An object of the present invention is to provide a disk drive and a head suspension unit in which the above-described problems are eliminated.
A disk drive according to the present invention comprises:
a disk which is rotated;
an arm module which comprises a plurality of plate-shaped arms which lie on top of each other;
a head slider which is supported by the extending end of the arm module and faces the disk; and
an actuator-which drives the arm module,
wherein the arm module has an arrangement in which the plurality of plate-shaped arms which lie on top of each other are integrated with each other.
A head suspension unit, used in a disk drive, according to the present invention comprises:
an arm module which comprises a plurality of plate-shaped arms which lie on top of each other; and
a head slider which is supported by the extending end of the arm module,
wherein the arm module has an arrangement in which the plurality of plate-shaped arms which lie on top of each other are integrated with each other.
In each of these arrangements, because the plurality of arms which lie on top of each other are integrated with each other, in comparison to a case where the plurality of arms merely lie on top of each other, the rigidity of the plurality of arms is higher. When the rigidity of the plurality of arms is higher, the resonance frequency of vibration of the plurality of arms increases, the amplitude of the vibration of extending ends of the arms when resonance occurs can be reduced, and the positioning accuracy of the head slider is improved.
Further, because the plurality of arms which lie on top of each other are integrated with each other, variation in the vibration characteristics among particular assembled arm modules is lower in comparison to cases of the related art, and is substantially eliminated. Thereby, the constants of the servo system which performs positioning of the head slider can be fixed, and high-accuracy positioning in a higher-frequency band can be performed in any one of assembled magnetic disk drives. Also by this reason, the positioning accuracy of the head slider is improved.
Further, as a result of the rigidity of the arms being higher, the extending end of each arm is unlikely to bend to approach the disk when shock is applied to the disk drive. Therefore, the extending end of each arm is unlikely to hit the disk, and, thereby, production of dust in the disk drive can be controlled. As a result, occurrence of a head crash can be avoided even in a case where the head slider floats above the disk with a small floating distance.
Overall, shock resistance can be improved and the storage capacity can be increased.
Each arm of the arm module may have a rib along a side edge thereof. Thereby, the rigidity of each arm becomes higher. As a result, the positioning accuracy of the head slider is improved, and shock resistance is improved.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of extending-end portions thereof being fixed to each other. In this arrangement, in comparison to a case where the arms are fixed to each other through the entire length thereof, manufacturing of the arm module can be easily performed.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of extending-end portions thereof being caused to adhere. In this arrangement, adhesive used for the adhesion exhibits a viscous damping effect. Thereby, the amplitude of vibration of the arms when resonance occurs decreases. When the amplitude of vibration decreases, the positioning accuracy of the head slider is improved.
The plurality of plate-shaped arms which lie on top of each other are integrated as a result of extending-end portions thereof being caused to adhere by using a piece of a double-sided tape.
In a case where arms are caused to adhere as a result of adhesive being coated, a work of coating the adhesive is needed. Also, the amount of the coated adhesive may vary, and, as a result, the characteristics of the thus-manufactured arm module may vary among particular products. In contrast to this, in the case where the piece of the double-sided tape is used for causing the arms to adhere, the portions at which the arms are caused to adhere can be made uniform, as a result of the size of the piece of the double-sided tape being controlled. As a result, it is possible to manufacture the arm module with little variation in the characteristics thereof. Also, the arm module can be easily manufactured. Further, a sheet and adhesive layers of the piece of the double-sided tape exhibit a viscous damping effect. As a result, it is possible to reduce the amplitude of the peak of vibration of the arms when resonance occurs. As a result, the head slider is positioned with high accuracy.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of extending-end portions thereof being welded together. In this arrangement, the extending end portions of the arms are firmly fixed to each other.
The disk drive may comprise a plurality of arm modules, each of which comprises a plurality of plate-shaped arms which lie on top of each other, the plurality of arm modules lining up vertically, and, except the lowest one, having openings through which a laser beam passes, respectively, the sizes of the openings of each pair of adjacent arm modules of the plurality of arm modules being such that the opening of the upper arm module is larger than the opening of the lower arm module,
wherein the plurality of arms of each arm module are integrated as a result of extending-end portions thereof being welded together by the laser beam which has passed through the openings of the higher arm modules.
In this arrangement, in the case where the plurality of arm modules line up vertically, it is possible to perform welding of the extending-end portions of the arms of each arm module after base portions of the arms are fixed. Thus, assembling of the head suspension unit can be easily performed. Further, no unnecessary stress is applied to the portions at which the arms are welded. As a result, the positioning accuracy of the head slider is not degraded.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of side faces of extending-end portions thereof being welded together. In this arrangement, because welding is performed from the side of the arms, welding is performed after the arms are caused to lie on top of one another and base portions of all the arms are fixed. As a result, no unnecessary stress is applied to the welded portions, and, therefore, the positioning accuracy of the head slider is not degraded. Further, the head suspension unit can be assembled with high work efficiency.
The plurality of plate-shaped arms which lie on top of each other may comprise two arms and may be integrated as a result of a projection formed on one of the two arms being press-fitted into an opening formed in the other of the two arms. In this arrangement, because work to be performed is mere press-fitting work, the arm module can be manufactured easily in comparison to the case where welding work is performed.
The plurality of plate-shaped arms which lie on top of each other may be integrated by using an eyelet member. In this arrangement, because work to be performed is mere work of inserting and deforming the eyelet member, the arm module can be manufactured easily in comparison to the case where welding work is performed.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of extending-end portions thereof pushing each other. In this arrangement, because adhesion work or the like is not necessary, the arm module can be manufactured easily.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of being fixed to each other through the entire length thereof. In this arrangement, in comparison to the case where only the extending-end portions of the arms are fixed to each other, the rigidity of the arms is higher.
The plurality of plate-shaped arms which lie on top of each other may be integrated as a result of extending-end portions thereof being fixed to each other and portions near to base portions thereof being fixed. In this arrangement, because also the portions near to the base portions of the arms are fixed, the rigidity of the arm module is higher.
The plurality of plate-shaped arms which lie on top of each other may comprise two arms, and a wiring path for a lead wire may be formed between the two arms. Because the lead wire is caused to pass through the wiring path, the lead wire is prevented from coming into contact with the disk.